Hydrangeas are popular plants, cherished for their showy blooms that add beauty to any garden. When planted directly in the ground, these shrubs can flourish for many years, offering diverse forms and colors.
Selecting the Ideal Site
Most hydrangeas thrive with morning sun and afternoon shade, as intense afternoon sun can scorch their leaves and cause wilting. Panicle hydrangeas (H. paniculata) can tolerate more sun if adequately watered, while bigleaf (H. macrophylla) and smooth hydrangeas (H. arborescens) prefer some shade. Protecting plants from harsh winds is also beneficial, and ensuring adequate space allows the mature plant to reach its full size without overcrowding.
Preparing the Soil
Hydrangeas prefer fertile, humus-rich, moist, and well-drained soil. Heavy clay soils can be amended with organic matter like compost to improve drainage and aeration, preventing root rot.
Soil pH significantly influences the bloom color of bigleaf (H. macrophylla) and mountain (H. serrata) hydrangeas. Acidic soil (pH 5.2-5.5) typically results in blue flowers, while alkaline soil (pH 6.6-7.5+) encourages pink or red blooms. Neutral to slightly acidic soil (pH 5.6-6.5) may produce purple or mixed blue and pink shades. White hydrangeas remain white regardless of soil pH.
To test your soil’s pH, use a home test kit or submit a sample to a local garden center or extension office. To encourage blue blooms, lower the pH by adding elemental sulfur or aluminum sulfate in early spring, aiming for a pH of 6.0 or lower. For pink blooms, raise the pH to between 6.5 and 7.0 by incorporating garden lime in fall or early spring. Follow product instructions carefully, as excessive aluminum sulfate can injure plants, and pH adjustments may take time to show full effect.
Planting Your Hydrangeas
The best times to plant hydrangeas are in late spring or early fall when temperatures are mild, allowing roots to establish before extreme weather. Dig a hole at least two to three times wider than the root ball, but no deeper than the root ball itself. This wider hole allows roots to spread easily into the surrounding soil.
Gently remove the hydrangea from its container. If roots are tightly circling, carefully loosen them or make a few vertical cuts on the root ball with a clean trowel to encourage outward growth. Position the plant in the hole so the top of the root ball is level with the surrounding soil, or slightly higher to prevent root rot. Backfill the hole with amended soil, tamping gently to remove air pockets. After planting, water thoroughly to settle the soil and provide initial hydration.
Ongoing Care and Maintenance
Consistent watering is essential for hydrangeas, especially during establishment and dry periods. Newly planted hydrangeas require deep watering daily for the first two weeks, then every other day for a few more weeks. Established plants typically need about an inch of water per week from rainfall or supplemental watering. Check soil moisture by inserting a finger about four inches deep; if it feels dry, water. Water deeply at the plant’s base to ensure moisture reaches the root system and to avoid wetting leaves, which can promote fungal diseases.
Fertilization supports robust growth and abundant blooms. A balanced, slow-release fertilizer with an NPK ratio like 10-10-10 or 12-4-8 is often recommended. Apply fertilizer in early spring as new growth begins, and a second application can be made in mid-summer, particularly for varieties that bloom on new wood. Avoid fertilizing in late summer, as this can encourage tender new growth susceptible to winter damage.
Pruning techniques vary depending on the hydrangea type, as some bloom on “old wood” (last year’s stems) and others on “new wood” (current year’s growth). Bigleaf (H. macrophylla) and oakleaf (H. quercifolia) hydrangeas bloom on old wood; prune them immediately after flowering in late summer or early fall to avoid cutting off next year’s buds. Smooth (H. arborescens) and panicle (H. paniculata) hydrangeas bloom on new wood and can be pruned in late winter or early spring before new growth emerges. For all types, remove any dead, damaged, or diseased wood. Deadheading spent flowers can improve appearance and encourage more blooms.
Troubleshooting Common Issues
Wilting leaves, particularly in the afternoon, often indicate a need for water, but they can also wilt from excessive heat or too much direct sun exposure. If the soil is consistently wet and leaves are droopy and discolored, it might be a sign of overwatering or poor drainage, which can lead to root rot. Improving drainage and adjusting watering frequency can help.
Yellowing leaves (chlorosis) can signal a nutrient deficiency, often iron, particularly in alkaline soils where iron is less available. Adjusting soil pH to be more acidic can help the plant absorb necessary nutrients. Lack of blooms can stem from insufficient light, improper pruning that removes flower buds, or damage from late frosts. Ensure your hydrangea receives adequate morning sun and prune at the correct time for its specific type.
Hydrangeas can experience common pests like aphids, spider mites, or Japanese beetles. A strong spray of water can dislodge many pests, and horticultural oils or insecticidal soaps can manage heavier infestations. Fungal issues, such as powdery mildew or leaf spot, may appear, especially in humid conditions or with poor air circulation. Spacing plants adequately, avoiding overhead watering, and ensuring good air flow around the foliage can help prevent these diseases. Removing affected leaves and applying an appropriate fungicide can also be beneficial.